1. Field of the Invention
The present invention relates to an extra-capillary (EC) fluid cycling system for a cell culture device, and more particularly to an EC cycling unit utilizing a non-rigid, EC reservoir fluidly connected to the cell culture device.
2. Description of the Related Art
The anticipated growth of personalized medicine will require new paradigms for the manufacture of therapies tailored to the needs of individual patients. The greatest challenge is expected to come in the area of cell based therapies, especially when such therapies are autologous in nature. In such cases each cell or cell based product will need to be manufactured from scratch for each patient. Manual methods for mammalian cell culture, by their nature, are prone to technician error or inconsistency leading to differences between supposed identical cultures. This becomes especially evident as more and more autologous cells are expanded for personalized therapies. Patient-specific cells, or proteins, are subject to variation, especially when scaled beyond levels that can be managed efficiently with manual methods.
In addition to being labor intensive, the stringent requirements for segregation of each patient's materials from that of every other patient will mean that manufacturing facilities will be large and complex, containing a multitude of isolation suites each with its own equipment (incubators, tissue culture hoods, centrifuges) that can be used for only one patient at a time. Because each patient's therapy is a new and unique product, patient specific manufacturing will also be labor intensive, requiring not just direct manufacturing personnel but also disproportionately increased manpower for quality assurance and quality control functions.
Moreover, conventional approaches and tools for manufacturing cells or cell based products typically involve numerous manual manipulations that are subject to variations even when conducted by skilled technicians. When used at the scale needed to manufacture hundreds or thousands of patient specific cell based therapies, the variability, error or contamination rate may become unacceptable for commercial processes.
Small quantities of secreted product are produced in a number of different ways. T-flasks, roller bottles, stirred bottles or cell bags are manual methods using incubators or warm-rooms to provide environments for cell growth and production. This method is very labor intensive, subject to mistakes and difficult for large scale production. Ascites production uses a host animal (usually a mouse) where the peritoneum is injected with the cells that express the product and are parasitically grown and maintained. The animals are sacrificed and the peritoneal fluid with the product is collected. This method is labor intense, difficult for large scale production and objectionable because of the use of animals. Another method is to inoculate and grow the cells in a small stirred tank or fermenter. The tank provides the environmental and metabolic needs and the cell secretions are allowed to accumulate. This method is costly in terms of facility support in order to do a large number of unique cells and produces product at low concentration.
Another method is to use a bioreactor (hollow fiber, ceramic matrix, fluidizer bed, etc) as the cell culture device in lieu of the stirred tank. This can bring facilities costs down and increases product concentration. Biovest International of Coon Rapids, Minn., has or had instruments using these technologies—hollow fiber, ceramic matrix, fluidized bed and stirred tanks.
Cell culturing devices or cultureware for culturing cells in vitro are known. As disclosed in U.S. Pat. No. 4,804,628, the entirety of which is hereby incorporated by reference, a hollow fiber culture device includes a plurality of hollow fiber membranes. Medium containing oxygen, nutrients, and other chemical stimuli is transported through the lumen of the hollow fiber membranes or capillaries and diffuses through the walls thereof into an extracapillary (EC) space between the membranes and the shell of the cartridge containing the hollow fibers. The cells that are to be maintained collect in the extracapillary space. Metabolic wastes are removed from the cultureware. The cells or cell products can be harvested from the device.
Known EC reservoirs have typically been rigid. They are a pressure vessel and therefore require a sealed compartment with tubing ports adding to costs. A gas, typically air, is introduced through a sterile barrier, generally a membrane filter, to control pressure in the vessel. Fluid level control has been limited to ultrasonic, conductive or optical trip points, or by a load cell measuring the weight of the fluid. Reservoirs are expensive and difficult to manufacture. There is limited EC fluid level measurement accuracy-ultrasonic, conductive or optical monitoring of fluid levels are commonly fouled by cell debris in the reservoir. Alternatively, load cells are not a rugged design for reliable fluid level sensing.
These methodologies rely on costly, labor intensive off-line sampling and analysis or additional equipment to interface with the instrument or require the addition of a lactate probe and electronics to the culture.
Preparing the system to start the cell culture is also very labor intensive. The cultureware must be assembled and sterilized or probes must be prepared, sterilized and aseptically inserted into the pre-sterilized portion of the cultureware. The cultureware assembly is then loaded onto the instrument. A series of manual operations are needed to check the integrity of the assembly, introduce fluid into the cultureware flow path, flush the toxic residuals from the cultureware, start the cultureware in a pre-inoculation mode, introduce factors into the flow path getting it ready for the cells, inoculating the cells into the bioreactor and starting the run (growth of the cell mass and eventual harvest of product).
Each unique cell or cell line must be cultured, cell products harvested and purified separately. In order to do a large number of unique cells or cell lines, a considerable number of instruments would be needed. If application of the cells or products for therapeutic purposes is contemplated strict segregation of each cell production process would be required. Consequently compactness of the design and the amount of ancillary support resources needed will become an important facilities issue. Moreover the systems currently available are general purpose in nature and require considerable time from trained operators to setup, load, flush, inoculate, run, harvest and unload. Each step usually requires manual documentation.
Accordingly, there is a need for an EC cycling device that is less expensive then the traditional rigid reservoirs and that provides accurate EC fluid level measurement.